A wide variety of active ingredients are currently known for treating various skin conditions. It is difficult to formulate many of these actives into cosmetically-elegant, oil-in-water systems because of stability, solubility, ionic strength, and other such formulation considerations. Representative of some of these active ingredients are materials such as salicylic acid, N-acetyl-L-cysteine, retinoic acid, phytic acid, and their pharmaceutically-acceptable salts.
For example, cosmetic compositions containing salicylic acid, N-acetyl-cysteine, and retinoic acid are known in the art. Salicylic acid and retinoic acid are keratoylic agents which are believed to help remove keratin plugs and to aid the skin's exfoliation process. These materials are also known for their anti-acne and anti-skin aging benefits. See C. Huber et al., Arch. Derm Res. 257, pp. 293-297, 1977; U.S. Pat. No. 4,888,342, to Kligman, issued Dec. 19, 1989; U.S. Pat. No. 4,877,805, to Kligtan, issued Oct. 31, 1989; PCT Application No. US-92-09739, Publication No. 0614354, to R. L. Blank, published Jun. 10, 1993; and PCT Application No. US-92-09737, Publication No.0614353, to R. L. Blank et al., published Jun. 10, 1993, which are all incorporated by reference herein in their entirety. N-acetyl-Lcrysteine is known for regulating wrinkles and skin atrophy (i.e. the thinning and general degradation of the dermis). See U.S. Pat. No. 5,296,500, to Hillebrand, issued Mar. 22, 1994, which is incorporated by reference herein in its entirety.
It has been found that the compositions of the present invention are well-suited for formulating and delivering a wide variety of active ingredients to the skin. Without being limited by theory, it is believed that these compositions contain gel network structures, liquid crystal structure, or both. It is believed that these gel networks and liquid crystals tend to bind the available water in the composition, thereby rendering the water less available for contributing to the instability and decomposition of the active ingredients. It is also found that these compositions are well-suited for carrying a high electrolyte concentration, making them ideal for delivering a wide range of ionic and other highly polar materials, e.g., zinc oxide, polar solvents.
Therefore, it is an object of the present invention to provide novel compositions for delivering a wide variety of active ingredients to the skin.
It is a further object of the present invention to provide water-containing compositions having gel networks, liquid crystals or both.
It is a further object of the present invention to provide water-containing compositions which can accomodate a high electrolyte concentration.
It is a further object of the present invention to provide stable compositions.
It is still a further object of the present invention to provide compositions which have acceptable aesthetic properties.
It is still a further object of the present invention to provide methods of treatment for a wide variety of skin conditions.